<html>
  <head>
    <script type="text/javascript" src="https://www.google.com/jsapi"></script>
    <script type="text/javascript">
      google.load("visualization", "1", {packages:["corechart"]});
      google.setOnLoadCallback(drawChart);
      function drawChart() {

        var options = {
          title: 'Wave form qr=60'
        };

        var chart = new google.visualization.LineChart(document.getElementById('chart_div'));
        draw_outputlevel(chart);
        var chart = new google.visualization.LineChart(document.getElementById('rate_div'));
        draw_rate(chart);
      }
    </script>
  </head>
  <body>
  	<p>Output level (in dB) for DX7 envelope, scaled from 0-99 output level values. This data is based on measurement of an actual device.</p>
    <div id="chart_div" style="width: 600px; height: 500px;"></div>

    <p>Similarly for rate, this time measured in dB/s, for decay. Attack is faster, and has a nonlinear curve.</p>
    <div id="rate_div" style="width:600px; height:500px"></div>
  </body>
  <script>

var outputlevel = [0, 5, 9, 13, 17, 20, 23, 25, 27, 29, 31, 33, 35, 37, 39,
41, 42, 43, 45, 46, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61,
62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80,
81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99,
100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114,
115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127];

function draw_outputlevel(chart) {
	var rawdata = [['value', 'gain']];
	for (var i = 0; i < outputlevel.length; i++) {
		var ol = outputlevel[i];
		var db = 20 * Math.log(2) / Math.log(10) * (ol - 127) / 8;
		rawdata.push([i, db]);
	}
	var data = google.visualization.arrayToDataTable(rawdata);
	chart.draw(data, {title: 'Output level to dB scaling', hAxis: {
		title: 'Output level value (0-99)'
	}, vAxis: {
		title: 'dB' 
	}});
}

function draw_rate(chart) {
	var rawdata = [['value', 'rate']];
	for (var i = 0; i < outputlevel.length; i++) {
		var qr = i * 41 / 64;
		var samplerate = 49096;
		var baserate = samplerate / (1<<20) * 20 * Math.log(2) / Math.log(10);
		var rate = baserate * (1 << (qr >> 2)) * (1 + .25 * (qr & 3));
		rawdata.push([i, rate]);
	}
	var data = google.visualization.arrayToDataTable(rawdata);
	chart.draw(data, {title: 'Rate values to actual level change', hAxis: {
		title: 'Rate value (0-99)'
	}, vAxis: {
		title: 'dB/s',
		logScale: true
	}});

}

  </script>
</html>
